Abstract.Birds
are unique among living tetrapods in possessing pneumaticity of the postcranial
skeleton, with invasion of bone by the lung and air-sac system. Postcranial skeletal
pneumaticity (PSP) has been reported in numerous extinct archosaurs including pterosaurs
and nonavian dinosaurs. Here we report a case of extreme PSP in a group of
small-bodied, armored sauropod dinosaurs from the Upper Cretaceous of South
America. Based on osteological data, we report an extensive invasion of
pneumatic diverticula along the vertebral column, reaching the distal portion
of the tail. Also, we provide evidence of pneumaticity in both pectoral and
pelvic girdles. Our study reveals that the extreme PSP in archosaurs is not
restricted to pterosaurs and theropod dinosaurs.